Mechanical allodynia in postherpetic neuralgia

Abstract

In 12 zoster patients who had developed postherpetic neuralgia with dynamic mechanical allodynia and in six zoster patients who had recovered without pain, the functional role of nociceptive C-fibers in allodynia was assessed by quantifying axon reflex reactions induced by histamine iontophoresis within allodynic regions and in their contralateral sites. In patients with postherpetic neuralgia, histamine responses were reduced or abolished within allodynic areas, indicating degeneration of nociceptive C-fibers. In patients who recovered without pain, histamine responses were bilaterally identical, indicating complete regeneration of nociceptive C-fibers. These results demonstrate that sensitized nociceptive C-fibers are not involved in signaling and maintenance of allodynia. Alteration in CNS processing may reorganize synaptic ties between central pain-signaling pathways and mechanoreceptive A beta-fibers depending on afferent C-fiber degeneration rather than ongoing C-fiber input.

Neurophysiological assessment of craniofacial pain

“…The neurophysiological findings in this patient receive support from supraorbital biopsy studies, indicating that this neuropathy predominantly affects the Aβ afferents and spares C fibres. This is an unexpected finding because these patients typically complain of constant burning pain, a symptom that in limb pains is usually attributed to C-fibre deafferentation [42].…”

Postherpetic Neuralgia: From Preclinical Models to the Clinic

“…29,30 Furthermore, functional studies investigating C-fiber axon reflex have demonstrated impaired or abolished chemically evoked antidromic vasodilatation in skin regions with intense dynamic allodynia, indicating a significant loss of cutaneous C-fiber afferents. 31,32 There is evidence that all sensory fiber types are affected in PHN, with constant pain possibly being associated with damage to nociceptive afferents and paroxysmal pain related to changes in A␤ fibers. 33 Quantitative thermal sensory testing showed greatly increased heat pain thresholds in the affected dermatome of some chronic PHN patients.…”

The role of stress in the development of herpes zoster and postherpetic neuralgia

“…The causes of postherpetic neuralgia are complex and thought to involve not only neural damage in the peripheral but also in the central nervous system [25]. The vulnerability-diathesis-stress model [3••] illustrates the role of stress in the development of postherpetic neuralgia (Fig.…”